Sawstop Inventor Still Struggling to Save Fingers

If you ever thought you had a great technical idea and wondered how easy it would be to get it accepted by industry, then you need to hear the story of Stephen Gass.

Gass, a former patent attorney with a PhD in physics, may finally be on the verge of changing the power tool industry. Then again, this isn't the first time he has believed that.

"It seems like, at long last, things may be breaking loose and moving towards the implementation of this technology," Gass told me recently. "It's more likely than not, but it's not a done deal."

To understand Gass's technological odyssey, though, you need to go back to the inception of his idea. Twelve years ago he conjured up a way of keeping table saws from cutting off the fingers of woodworkers. Using a capacitive technique to sense a drop in voltage whenever the blade teeth contacted salty wet tissue, Gass's saws "recognized" potentially dangerous situations. Within a few thousandths of a second, they could engage a spring-brake, stop a blade dead in its tracks, and save a digit or two. On his company's Website you can watch a video demonstration of this (on a hot dog).

Stephen Gass’s Sawstop system reportedly has saved more than a thousand fingers that have touched the saw blade. Source: Sawstop LLC

Gass, of course, believed in 1999 that he had come up with a significant idea. According to statistics from the US Consumer Product Safety Commission, approximately 30,000 people per year were being injured by table saws, with about 10 percent of those accidents involving amputation. Gass saw his idea as a way to deal with that loss of fingers.

Still, not everyone agreed. Power tool manufacturers, quite understandably, saw the concept as a manufacturing nightmare. They balked at the possibility of having to invest frightening amounts of capital to retool existing production lines. Moreover, lawyers viewed it as an enormous product liability problem. What if it didn't work and someone lost a finger? Worse, what if it did work? Would it mean the manufacturers would be now legally liable for all other saws that didn’t use the new technology?

Legal experts were clear on one point when it came to table saws. The unwritten rule says, "Use it at your own risk." Because adult users understood the propensity for sharp edges to cut, the saw makers were legally protected. For them, the brutal status quo made a lot of sense.

During the initial seven years after Gass invented the technology, power tool manufacturers butted heads with him. They claimed his idea didn’t work. They complained it was too expensive. They argued that his licensing fees were exorbitant. They said his technology would create a monopoly.

Then, in 2006, the US Consumer Product Safety Commission (CPSC) shocked the industry by recommending the government begin a "rulemaking process" requiring that future saws incorporate an active injury mitigation system. We wrote about this five years ago when Gass thought he’d been vindicated.

But it turned out to be just another bump on a very rocky road. A week after the Commission voted in Gass's favor, the chairman, whose vote had been critical, retired. And the battle resumed.

This important safety story reminds me of seat belts, shoulder-harness seat belts, and air bags. All of those developments were around years before they were widely adopted. Of course, as you point out here, there's a little bit more involved in terms of retooling. Still, you'd think the prospect of spare digits (not to mention, prevention of deaths) would be something that'd get customers crying out to the vendors to implement this great feature. (Everyone should see that video.)

This should help prevent accidental injuries and hopefully there is a measure in place to prevent tampering of the safety device. This article should be tied into the common sense article. Safety is only as good as the person using the tool.Engineers can always design safety into the equipment, but in the end it comes down to the operator.

Given the attention the Sawstop and Stephen Gass has gotten over the years for this exciting invention, is it a stretch to think that power tool manufacturers might jump on acquiring or licensing the technology? Especially if there are signs of possible regulation pending that might mandate similar safety functionality. I would think there would be plenty of opportunity there unless Gass prefers to hold out.

Yes, I've followed this story as well, and I'm surprised some manufacturer hasn't grabbed this technology to give its products a competitive edge -- especially since this story is getting around and there is likely some pent-up consumer demand. Maybe that's the push is needs, a producer willing to incorporate the technology and test it on the upper end of the saw market. I've heard $99 quoted as the additional cost of incorporating Gass's technology. And apparently it works.

One application I could see for this product would be in aluminum foundries. Traditionally, band saw operator is one of the first jobs for new employees. It's also one of the more dangerous. Installing a Sawstop would be much cheaper than a robotic cut-off cell, and the savings in terms of lost work time, workman's compensation, insurance, medical costs, etc. would easily justify it. Plus, it might just help a foundry win some goodwill from OSHA.

Maybe instead of focusing on home power tool manufacturers, Gass should focus on industrial users. As T.J. pointed out in another thread, under the U.S. legal system, the employer as well as the equipment manufacturer are liable in industrial accidents, since the employer has the responsibility to provide a safe workplace. If the equipment manufacturers are resisting this technology, maybe the employers will be more receptive.

I don't believe this technology works for metal cutting applications since it is sensing the change in capacitance created by the blade touching a water filled object (you). If you are cutting a metallic object then the blade is already grounded through the metal object and there will be no change to measure.

About the issue of mandating this on new saws. There is a perverse effect of unintended consequences. The most menacing wood working shop tool would have to be the shaper, yet they tend to have the lowest injury rates. Why? Two-fold, for starters only the more experienced woodwork is willing to invest in a shaper so hopefully being more experienced he is also more careful. But I believe the most important reason is that by their very design shapers scare the crap out of the user which makes them a lot more cautious and deliberate in their use.

The same effect happens in traffic. A wider, safer looking residential street encourages speeding which in turn increases car/pedestrian accident rates. That is why the current trend is to restrict (narrow) streets that have a lot of car/pedestrian accidents to make drivers less comfortable and slow down. If adding sawstop technology makes a table saw seem less dangerous to the user then it will most likely result in increased injury rates rather than reduced injury rates. While blade cuts from table saws are common they are mostly superficial. The most common serious table saw injuries are caused by kick-back.

I have been following SawStop news for years. This is great technology for industry and the home wood worker! It's good to know that he may be gaining more acceptance. Besides the litigation aspects, I imagine that this comes down to the numbers, 30,000 injuries a year may be very small compared number of saws sold annually. As in the pharmaceutical industry, a new drug is not worth developing unless profit can be realized from millions of new customers. Perhaps in the near future Mr. Gass can reduce the cost of the system to make it more appealing to the masses.

Sharp blades spinning at a high rate of speed are dangerous. This is key to any cut off fixture design. For manufacturing, the two main focuses are the cut off operation and then protecting the operator from the cut off operation. There should be no reason why this mentality should not carry over into the consumer market. The standard (cheap) solutions from saw manufacturers have been splitters and saw covers. These are cumbersome and block view of the blade. They are also easily removed which defeats their purpose. Upgrading to the Sawstop technology will put a non-removable safety technology on a very dangerous piece of equipment.

Two somewhat contradictory comments from an engineer and amateur wood hacker. First of all, what Stephen Gass and Sawstop have done is fantastic. Not only does his invention work (have you seen the demo where someone actually places their finger on the line! No - not the hot dog but someone (Mr. Gass?) actually puts their finger in front of an operational blade!) but the tablesaw itself is a darned good one. IF I had the money and the space and the need for a new table saw, I would certainly buy one.

So the saw itself is a darned good saw and the blade stopping safety mechanism works and works well.

BUT (you knew there had to be a but) should all saws be required to have this type of technology? I'm not at all sure. A lot of accidents where folks lose a finger or two to a spinning blade are their own fault because they don't use the saw the way they should. They defeat/remove the saw guard, they get zero training on the saw, etc. It is truly amazing the number of ingenious ways people think of in order to get their fingers down there in the danger zone.

By mandating a 'stop the blade' mechanism, we will be increasing the cost of a table saw rather substantially. I'm guessing that if the Bill of Material cost went up by $100, the selling price would go up $200 - a big jump for a $400 table saw and prohibitive for a $200 table saw. If I had my druthers, I would pay the price but I think a lot of people would be a bit unhappy.

None the less, the sawstop technology is fantastic and the gumption of Stephen to produce a new saw (actually a line of saws) incorporating this technology is wonderful. A great saw and a great accomplishment.

A friend in the power tool industry obtained a video of the Sawstop in action when it first came out and it was clear to see the massive level of stress that was applied to the rotating parts - that was enough for me to question the viability of such a device considering the increased level of secondary risk. I think it's a great concept but agree with everyone else that a friction brake assembly would be far safer and at least somewhat easier on the equipment. As for the triggering mechanism, most of the places I've worked would be considered "extreme environments" (water, snow, ice, mud) which also means gloved hands and thus rendering any such trigger device pretty much worthless. I'm not opposed to the concept, it just needs a lot more work.

BobGroh commented on guards being removed - you'll find that on some of my equipment too and for the reason that the guards often create more of a hazard than anything. A few months ago I used a Delta brand table saw owned by one of my clients and I removed the guard after the first cut because it created a serious kickback issue. I have an older Crapsman radial arm saw that I removed the anti kickback device because it would engage in a climb-cut condition increasing the effects of the climb and kickback making any kickback far more dangerous. Guard on table shaper was removed because the guard spring forced the work into the cutter at the start of the cut - heavy work would get sucked into the cutter knocking the snot out of anything in its path (namely me). I'm not opposed to guards, I'm just opposed to guards that are more of a safety hazard than the equipment itself. Mark

The use of the 'sudden stop' mechanism on the SawStop is the genius part of the system. You absolutely must have something that reacts RIGHT NOW - in milliseconds - I don't think a friction brake or the like would do the job. If you watch the SloMo shots on the mechanism you can see that the inventor does 2 things when a 'delicate part' is sensed - the SawStop jams the blade off AND jerks the whole blade assembly down and into the interior of the saw. It is impressive AND it works.

After a 'stop incident', you have to replace the entire saw stop and retraction mechanism (which I understand is a $100 or so expense). Frankly I would be more than willing to pay for the new assembly in such a case! After all, my finger/fingers/hand were just saved.

The saw stop and retraction mechanism is rather nicely designed to absorb the energy with a controlled collapse of the control arm and a few other niceties. Very well done.

And, yes, you still have to cope with other causes of accidents like kickbacks. But at least the chances of cutting off a piece of 'you' is greatly diminished.

I'm not arguing the value of added safety but rather the one-time use of the design. Consider GFCI's, if not for being easily reset without additional cost beyond some annoyance from false trips, they would not have been so readily accepted for use. Same applies to the Sawstop, if it were not a destructive one-time use device, I think it would find a much wider acceptance.

Consider a common motor-mounted friction brake can stop a 300# mixer paddle within 30° of rotation, the same can be done with the far less mass of a saw. Same with the drop-down, such can be done with the need to stop rotation as once the blade is below the deck, it no longer poses a threat. The drop can be done with a system that easily reset and doesn't cause undo damage to the machine.

I understand the arguments against this technology. But this is a technology that should come down in price and spread to more types of saws in the coming decades. It's still in its infancy today. When I talked to Gass last week, he said, "I like to imagine that 30 years from now, people will tell their kids about how saws could cut your fingers off back in the old days. It will be comparable to talking about how bleeding people was once an accepted medical treatment."

A great invention and some manufacturers are using it. As a woodworker, I thought it was a great idea but:

When the invention first came out, Mr Gass tried to get a mandate that all manufacturers must use his technology which gave the appearance that he was not really interested in personal safety, he was just trying to force all manufacturers to pay him licensing fees.

The early version could false detect and Sawstop destroyed your saw. Cutting green or wet wood could result in a destroyed saw. Most woodworkers loved the concept but not the implementation. If these issues have been fixed, I would choose a saw with Sawstop. The operative word is choose. An invention should go to the market, not to the legal system, for acceptance.

I am amazed by the comment from Timmmmy49. He evidently believes that all of us are so stupid that we must be protected by purchasing this sawstop system.

I agree that it is a remarkable invention, and quite an achievement. Now I would invite mr timmmmy to explain to us how we can continue to use the saw after this device triggers. Please explain the reset process, OK? The fact that is not explained is that after the device is triggered, a portion of the mechanism must be replaced, and possibly the blade must also be replaced. To make it even less convenient, the replacement parts will only be available from one source, and they will probably not be cheap. In addition, consider the location of the device inside the saw mechanism, which will not be an easy or convenient place to do any work at all.

I agree that persons such as mr timmmmy should never ever be allowed to do anything that may possibly be dangerous, since they may be injured. But, as an American, I believe that I am free, and that I should not live my life enslaved by the fears of others.

One more thing: every day more people may be killed in transportation accidents than are injured by power saws. Sometimes the results are woth the risk.

This comment is not intended to be inflamitory, but rather to point out that some of us do not wish to have our lives run by those who are in a constant state of fear.

I think that the delays are just tactics the companies are using to wait out the patent on Sawstop. That way they can design it however they like and maybe come up with something better. Isn't there only 5 years or so left in the patent protection?

The design isn't really rocket science--just the fancy electronics to sense the flesh getting close to the blade. One of the comments mentioned nuisance trips of the sawstip when cutting wet wood--presumably related to the sawstop not being able to differentiate between wet wood and flesh (or hot dogs!) So the sensing method probably should be considered for improvement, too.

The rest of the system is the braking method. (the article mentioned a "spring brake") It is only really good for small, low inertia saws such as used in cutting wood up to 12" in diameter or so. Don't shoot the messenger! It's the physics of the situation. Stopping a blade dead in a few milliseconds from a surface speed of several thousand feet per minute is no mean feat unless the inertia of the moving system is low.

Consider using this on a larger diameter circular saw or on a bandsaw where the two bandsaw wheels look like big flywheels when trying to stop. Your braking system starts to look pretty humoungous. I shudder to think what might happen if instant stopping is mandated for big industrial saws--kind of like making a law that pi will be exactly 3!!!

Emergency stopping of larger industrial blades might be worth trying if there is no better guarding method that keeps operators out of harms way. However, it will more likely be a "damage reduction stop" where the blade is stopped quickly, but not quickly enough to prevent a few teeth from cutting the hot dog. In my game, (sawmilling) personnel are not even close to large blades so it's a non-issue, except for stopping them at break times to change blades. Then DC injection braking is usually used for a non-emergency stop. The high inertia machines can take many minutes to stop, even with hundreds of amps of DC braking current.

I can see power tool manufacturers offering their version of sawstop as a different model--for example Makita has been offering an electric hand saw with or without an electric brake for many years now.

The sawstop system is absolutely an incredible setup, snd it is able to stpo the larger blades "instantly". The setup that I saw a photo of has a quite strong aluminum alloy arm with some large steel pins well anchored into the arm. When the system is triggered these pins are forcfully jammed int the sawblades teeth. It is a violent metal to metal impact. It is not a frictin brake sort of stopping, it is not even as gentle as ramming a car into a bridge abutmaent.The stop is a lot more like a rod-through-the-spokes stop on a bicycle. So the blade would be stopped befor much damage could be done to a finger. The damage to the saw and the mechanism is not explained, nor is the detail of replacing the actuator trigger device described in any detail.

I would ask a question, though, which is, "how well does it work with the fine-toothed saws, such as some veneer blades?" My impression is that the steel pins engage the deep notch below the leading edge of the individual teeth. How would that function with a finer-toothed blade?

William, you are correct....the sawstop, even though it mentions a "spring brake" in the blog copy, uses a bunch of different methods of stopping.

I did a quick Google patent search and found interestingly, that Gass has quite a few patents in the field, but so does Black and Decker, which seem more recent than Gass. One B&D patent I scanned had well over 100 figures, so it is pretty obvious that they are trying to tie up the subject very thoroughly. Some of the Sawstop patents are dated 2000, so he has precious little time to capitalize on them before they expire. I suspect that there will be lawsuits up the wazoo if this gets mandated!!

The stopping methods vary from gentle (a brake) to destructive (release of compressed gas to do something like the tossing a pipe into the spokes). The was a bandsaw brake that looked like it might simply cut the blade when stopping, which is a slick way of getting around the intertia issues of the bandwheels. I would be pretty peeved if I had "nuisance trips" with this kind of destructive saw brake! I doubt that Mr sawstop has been in a sawmill when a 12" wide bandsaw blade, 40 feet long, parts at 10K feet per minute.

The website talks about an accident happening every few minutes where someone gets their fingers in the blade. Question I have is what is going on in these injury cases. How many of these like in the case of drunk driving were the result of impairment in the woodshop? Drinking a few beers while running the saw is dangerous!!!. Now if we get Sawstop can we drink and run the saw and be safe? Put the beers up while running the saw. Perhaps a breathalyzer test that prevents the saw from starting up under the influence would work just as well at preventing injury. What do you think?

In the video of the hotdog, the blade is set awful high up. We were taught to keep the blade no more than 1/4 inch above the top of the wood being sawed to reduce risk of injury.

Stopping the blade that quickly is bound to put a lot of stress onto it. What is the risk of the blade shattering and metal shards flying out over the workplace?

It's a great product, but I think more thought could go into it and improve it in several details.

As an equipment designer and a frequent user of all kinds of saws, I cannot imagine how this idea just will not go away. It sounds like a bright idea until you find out that it intentionally destroys the equipment.

Obviously, it would be applauded by a few who believed that they were "saved" by it, but how many false positives are there going to be that lead to the complete destruction of very expensive machines for non existent problems.

Sorry, but I for one am not buying it! Like most everything we do in life, handling a saw is a calculated risk. I accept that as is.

I design control systems, drive cars, rig antennas and go SCUBA diving in the ocean, all of which have a degree of risk...and yes I frequently use a table saw and without the guard.

I teach people about the use of a table saw in simple terms. You just think of the blade as a rattlesnake and as soon as you take you eye off of it, you will get bit!

Well I think the problem you all seem to have stems from the fact that you haven't used one. I have. It is a beautiful machine. there aren't "false positives" all the time. maybe hardly ever. The safety system can be bypassed to cut conductive materials. It runs just as well as or better than any powermatic or delta as far as I'm concerned.

To say the false positives aren't worth the risk reduction either means you aren't thinking clearly or you just don't value the possibilities of suffering. A big table saw costs 4 grand. sure, that's a bit of money. But I use a table saw every day and my shop brings in hundreds of thoiusands of dollars a year. so how expensive is it really? maybe for weekenders.

Good question-- How many false positives would destroy equipment for no reason? Unfortunately for your argument, that's not a rhetorical question, it has an answer. Ask anyone who uses one and I think you'll find there are hardly any at all. The system is quite good. I know because I've used one for a considerable amount of time. have you? And by the way, how many destroyed table saws equals a hand lost. one? ten? forty? a hundred? How much would I have to pay you to let me cut off your hand? Would you take a million? Do you even know what it's like to live without a hand?

Suppose the saw had a false positive once a year. (Which it wouldn't. I know, because, again, I've used one) Even If I had to buy an entirely new saw every year, isn't that worth the thirty thousand dollars when I still have a hand at year ten when that accident does happen, after I'm thirty grand in? Definately! And besides that, it would probably be a wash compared to the cost of amputatiing my mangled hand.

You are all caught up in the "machine". The machine has to be built to last. I'm sorry but that's ignorant. Hands are more important. Machines are for the benefit of humans. And they don't last anyway. The bottom line is that machines can be replaced so easially...hands cannot. I can't beleive I'm saying this isn't it obvious?

You're arguing in the abstract. come out here in the real world where people run a saw day in and day out. come out here where hands go away and never come back. come out here where saws are tools, not idols. Come out here where they don't ultimately cost that much. Come out here where saw stop saws are being used every day and all the terrible things you say about them aren't happening. You're right. They just won't go away.

BTW to say that using a saw is a calculated risk that one must accept is so silly. It doesn't have to be as big a risk. duh.

As someone who uses a table saw every day, I certainly hope someone as dumb as you isn't teaching anyone anything.

And I bet you felt pretty good about yourself telling off all those sissys who want to keep their fingers.

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